Sheet post-processing apparatus

ABSTRACT

In an apparatus that performs saddle-stitching processing of a sheet pack, a pair of folding rollers is arranged in such a manner that large-diameter parts and small-diameter parts are alternately formed and that the large-diameter parts are abutted against the small-diameter parts at a facing part symmetrically about the center of a transport passage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a sheet post-processing apparatus having saddle-stitching processing and folding processing functions, and particularly a sheet post-processing apparatus that can realize highly accurate folding processing.

2. Description of the Related Art

A sheet post-processing apparatus has been proposed that has a bookbinding function to bind, with staples, plural sheets on which images have been formed. As binding methods carried out in such a sheet post-processing apparatus, there are edge-stitching of stitching a sheet pack at one position or plural positions on its edge side, and saddle-stitching of stitching a sheet pack at plural positions in its central part. Some apparatuses that carry out saddle-stitching have a saddle-stitching and folding function of folding a stitched sheet pack at its central part into a weekly magazine shape.

In this saddle-stitching and folding function of folding a stitched sheet pack at its central part into a weekly magazine shape, a folding unit at the central part is formed by a folding knife and a pair of folding rollers (for example, JP-A-2005-8418).

The folding unit at the central part of a sheet pack is to push the central part of the sheet pack that has been transported, to facing parts of the pair of folding rollers by the folding knife, and to perform bending processing to the sheet pack by pressurization due to the rotation of the folding rollers.

Also, as a method for removing wrinkles generated in a direction perpendicular to the transport of the transported sheets, a technique of flexing the sheets in a direction perpendicular to the transport of the sheets by using a corrugation roller and thus removing wrinkles is disclosed (for example, JP-A-7-10345).

However, in the case of pushing a sheet pack to the facing parts of the pair of folding rollers and performing bending processing to the sheet pack by the folding rollers, the folding force (pressurization activating force) to the sheet pack is active only in a linear grounding area of the facing parts of the pair of folding rollers where the folding surface of the sheet pack faces. Therefore, the activation of pressurization causes linearly equally distributed load. Thus, to achieve sharp folding of the sheet pack with high adhesion, the adhesion pressure (press-contact force) of the pair of folding rollers must be extremely high and the linearly equally distributed load must be high as a whole. Otherwise, sharp folding processing with desired adhesion cannot be carried out.

If desired sharp folding processing with good adhesion cannot be carried out, the inward part of the folded sheet pack SP is higher as shown in FIG. 9. Also, since the folded sheet pack SP are not adhered to each other, it is not firm at all in the direction of transport as shown in FIG. 10, causing a problem that jamming is generated during the transport.

Also, in the case of the corrugation roller, wrinkles can be removed for a small number of sheets, but it cannot achieve a folding effect to sharpen the folding of the sheet pack itself.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sheet post-processing apparatus having a pair of folding rollers for folding a sheet pack at its center.

In an aspect of the present invention, a sheet post-processing apparatus includes

a stitching processing unit configured to stitch a sheet pack transported in a transport passage, at predetermined plural positions in along a straight line orthogonal to the direction of the transport with a stitching needle,

a pair of folding rollers arranged on a stage following the stitching processing unit in the transport passage, in which large-diameter parts and small-diameter parts of the respective folding rollers are alternately formed symmetrically about the center of the transport passage, and in which facing parts are arranged at the central part in the transport passage so that the small-diameter parts are abutted against the large-diameter parts, and

a folding unit having a paper folding plate configured to push the sheet pack into an abutting part of the pair of folding rollers.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a sheet post-processing apparatus as the best embodiment to carry out this invention.

FIG. 2 is a perspective view showing the positional relation between a sheet pack and a paper folding plate when the sheet pack is stopped at a predetermined position in the sheet post-processing apparatus of this invention.

FIG. 3 is a side view in the case of performing folding processing to a sheet pack in the sheet post-processing apparatus of this invention.

FIG. 4 is a perspective view showing the relation between the paper folding plate and folding rollers for performing folding processing in the sheet post-processing apparatus of this invention.

FIG. 5 is a side view of a mechanism for driving the paper folding plate in the sheet post-processing apparatus of this invention.

FIG. 6 is an explanatory view of the shape of the folding rollers in the sheet post-processing apparatus of this invention.

FIG. 7 is a side view showing the pressing position of the paper folding plate and the movement of a sheet pack in the folding processing in the sheet post-processing apparatus of this invention.

FIG. 8 is a side view showing the state when performing the folding processing while fixing a sheet pack with a paper discharge guide plate in the sheet post-processing apparatus of this invention.

FIG. 9 is an explanatory view showing trouble in a conventional sheet post-processing apparatus.

FIG. 10 is an explanatory view showing trouble in a conventional sheet post-processing apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and methods of the present invention.

Hereinafter, the best embodiment to carry out this invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a sheet post-processing apparatus 2 as the best embodiment to carry out this invention. This sheet post-processing apparatus 2 has a simplified bookbinding function of receiving sheets on which images have been formed by an image forming apparatus 1, performing staple processing, and folding a stapled sheet pack SP.

As shown in FIG. 1, the sheet post-processing apparatus 2 includes a entry guide plate 201, feed rollers 202, 203, a branching pawl 204, a discharge feed roller 205, a staple tray 402, a staple tray feed roller 209, a paddle 210, a sheet rear end receiver 421, a saddle-stitching stapler 403, transport rollers 211, 232, a paper discharge guide plate 231, a paper folding plate (stitching needle abutting member) 466, folding rollers 451, 452, and a paper discharge tray 301, arranged along a transport passage in which a sheet pack SP is transported.

First, the operation in the sheet post-processing apparatus 2 after receiving sheets from the image forming apparatus 1 will be schematically described. The sheets discharged from the image forming apparatus 1 are guided to the transport passage in the apparatus by the entry guide plate 201. The sheets are transported by the feed rollers 202, 203, and sent to either a transport passage for discharge or a transport passage for staple processing, by the branching pawl 204.

When the transport passage for staple processing is selected, the sheets are sent to the staple tray 402 by the staple tray feed roller 209, and here the sheets are dropped one by one below the staple tray 402 by the paddle 210. The sheets dropped by the paddle 210 are received by the sheet rear end receiver 421 and the rear ends of the sheets are aligned with each other. The alignment in the direction of the width of the sheets (the direction orthogonal to the sheet transporting direction) is carried out by a lateral alignment plate, not shown. In this case, in the state where a saddle-stitching staple mode is selected, the transport roller 232 is situated at a position away from the transport roller 211 by the turning of the paper discharge guide plate 231.

In the case of saddle-stitching operation, after the last sheet is aligned, saddle-stitching processing of the sheet pack SP is carried out at two positions thereon by two saddle-stitching staplers 403 provided at a predetermined spacing in a horizontal direction. The stitching positions are on a line that lies at the center of the sheets in the same direction as the sheet transporting direction.

Then, the sheet pack SP is lifted up by a pack takeout belt, not shown, and it is stopped when the stitching staples from the saddle-stitching staplers 403 have reached predetermined positions.

FIG. 2 is a perspective view showing the positional relation between the sheet pack SP and the paper folding plate 466 in this case. In the transport operation by the pack takeout belt, the paper folding plate 466 is waiting at a position away from the sheet pack SP as shown in FIG. 2.

After that, operations described below by the transport rollers 211, 232 and their peripheries, and the paper folding plate 466 are carried out to the sheet pack SP, and the central part of the sheet pack SP is pushed in between the folding rollers 451, 452 by the paper folding plate 466 as shown in FIG. 3. After simplified bookbinding processing is thus carried out, the sheet pack SP is discharged to the paper discharge tray 301.

On the other hand, in the case where the transport passage for discharge is selected as the destination of transport of the sheets received from the image forming apparatus 1, the sheets are sent toward the discharge feed roller 205 by the branching pawl 204, then sent to the transport rollers 211, 232 by the transporting force of the discharge feed roller 205, and directly discharged to the paper discharge tray 301. The operations of the respective parts in the sheet post-processing apparatus 2 are controlled by a control unit, not shown, in accordance with input of instructions from the user.

Next, the configuration of the folding processing unit will be described. FIG. 4 is a perspective view of the paper folding plate 466 and the folding rollers 451, 452 for carrying out folding processing. FIG. 5 is a side view of a mechanism for driving the paper folding plate 466. The paper folding plate 466 in the form of a thin plate is provided to be movable in the direction of the arrow along a guide slit 465 by fitting a shaft part 464 integrated with its lower surface into the guide slit 465. The rotational driving from an output gear 461a of a paper folding plate driving motor 461 is transmitted to a cam 467 via an intermediate gear 462, thus causing the cam to turn forward and backward. A link 463 has its one end rotatably and axially supported by a shaft part 462 a of the intermediate gear 462, and has the one shaft part 464 loosely fit in an elongate slit provided at its other end. A pin 467 a provided in the cam 467 is axially supported at a middle part of the link 463. The forward and backward turn of the cam 467 causes the link 463 to rock between the position indicated by the solid line and the position indicated by the dotted line. Thus, the paper folding plate 466 linearly reciprocates in the direction of the arrow.

The paper folding plate 466 also has protruding parts 466 a, 466 b, 466 c at its distal end. The protruding parts 466 a and 466 c are provided at the same positions as the staple positions of the saddle-stitching stapler 403. The protruding part 466 b is provided at the center between the two staple positions of the saddle-stitching stapler 403. The purpose of providing the protruding parts 466 a, 466 b, 466 c at three positions is to cope with the flexure of the sheet pack SP and generation of wrinkles at the central part in the folded state due to incomplete pressing of the sheet pack SP to the folding rollers 451, 452, which would occur in the case where the protruding parts are provided at two positions on the paper folding plate 466.

As shown in the appearance view of FIG. 6, each roller of the pair of folding rollers 451, 452 is a stepped roller with a step of approximately 1 to 2 mm, and has a shape in which large-diameter parts 451 a, 452 a having a large roller diameter, and small-diameter parts 451 b, 452 b having a small roller diameter are alternately arranged symmetrically about the center CL of the transport passage. Moreover, these are arranged so that the facing parts of the folding rollers 451, 452 to each other have different diameters. That is, the large-diameter parts 451 a, 452 a of the one folding roller 451, 452 face and are abutted against the small-diameter parts 451 b, 452 b of the other folding roller 451, 452.

Also, the large-diameter parts 451 a, 452 a or the small-diameter parts 451 b, 452 b are arranged symmetrically about the center CL of the transport passage.

Therefore, at the center CL of the transport passage, a combination of the large-diameter part 451 a, 452 a of the one folding roller 451, 452 and the small-diameter part 451 b, 452 b of the other folding roller 451, 452 is constantly arranged. Moreover, the width of the large-diameter parts 451 a, 452 a and the small-diameter parts 451 b, 452 b arranged at the center CL of the transport passage is smaller than the width of the minimum sheet pack SP transported in the transport passage. Each folding roller 451, 452 is formed so that the total of the large-diameter parts 451 a, 452 a and the small-diameter parts 451 b, 452 b is at least three or more.

The folding rollers 451, 452 are configured to be rotationally driven in both directions by the driving of a driving gear pulley 455, intermediate gears 456 and a following gear 457 via a timing belt 454 in accordance with the driving of a folding roller driving motor 453. The driving gear pulley 455, the intermediate gears 456 and the following fear 457 are connected by arms 458, 459 and are configured to be movable between relative positions with respect to each other while maintaining their respective axes. Thus, in the state where the sheet pack SP is inserted between the folding rollers 451, 452 and the rollers are moved away from each other, the rotational driving can be securely transmitted to both folding rollers 451, 452. Also, the folding rollers 451, 452 are pressed in contact with each other by a tension spring (not shown).

The protruding parts 466 a, 466 b, 466 c at the distal end of the paper folding plate 466 press the positions of the staples stapling the sheet pack SP, and move forward to the position that overlaps the nipping position of the folding rollers 451, 452, thus carrying out folding processing to the central part of the sheet pack SP by the press contact and rotation of the folding rollers 451, 452.

In this case, both of the folding rollers 451, 452 are stepped rollers with a step of approximately 1 to 2 mm and are arranged in such a manner that the facing parts of the folding rollers 451, 452 to each other have different diameters. Therefore, the sheet pack SP nipped and pressed between the pair of folding rollers 451, 452 is bent at the parts where the combination of the large-diameter part 451 a, 452 a and the small-diameter part 451 b, 452 b of the folding rollers 451, 452 facing each other changes into the opposite combination, and dot-like pressurizing points P are generated there. The sheet pack SP receives concentrated load due to the pressurizing points P and is strongly bent by the concentrated load. Therefore, sharp folding with adhesion can be achieved. Also, since wrinkles on the sheet pack SP are expanded at the same time, a wrinkle removing effect can be achieved, too.

In this case, if the number of the large-diameter parts 451 a, 452 a and the small-diameter parts 451 b, 452 b of the respective folding rollers 451, 452 is increased, the pressurizing points P can be increased accordingly.

At the parts of the sheet pack SP nipped between the protruding parts 466 a, 466 b, 466 c of the paper folding plate 466 and the folding rollers 451, 452, the folding state is worse by the amount equivalent to the thickness of the paper folding plate 466 because the pair of folding rollers 451, 452 cannot be directly pressed in contact thereto. As for the folding state at the staple positions, the folding is worse than the parts having no staples because of the thickness of the staples. Therefore, if the protruding parts 466 a and 466 c of the paper folding plate 466 coincide with the staple positions on the sheet pack SP, the positions with the poor folding state coincide with the staple positions and the minimum folding state can be secured.

Also, in the operation in which the protruding parts 466 a, 466 b, 466 c of the paper folding plate 466 press the sheet pack SP and move forward to the position that overlaps the nipping position of the folding rollers 451, 452, thus carrying out folding processing to the central part of the sheet pack SP by the press contact and rotation of the folding rollers 451, 452, the protruding parts 466 a, 466 b, 466 c of the paper folding plate 466 that have moved forward need to retreat from the pressurizing state between the folding rollers 451, 452 and the sheet pack SP. In this case, since only the protruding parts 466 a, 466 b, 466 c of the paper folding plate 466 are nipped between the folding rollers 451, 452, the frictional force of the folding rollers 451, 452 is small because of the small area, and the load on the driving unit at the time of retreat can be small.

Then, after the driving motor of the transport rollers 232, 211 has stopped, the rotation of the driving motor is locked, thereby fixing the distal end of the sheet pack SP. As the transport rollers 232, 211 are locked, the fixation of the sheet pack SP by the paper discharge guide plate 231 can be secured.

Next, as shown in FIG. 7( a) and (b), the sheet part directly above the stitching staple is pushed by the paper folding plate 466, and while the distal end of the paper folding plate hooks the staple on the fixed sheet pack SP and thus receives resistance due to friction, the paper folding plate pushes the sheet pack toward the nipping part of the folding rollers 451, 452, as shown in FIG. 7( c).

As shown in FIG. 8, since the distal end of the sheet pack SP is fixed by using the paper discharge guide plate 231, the shift of the sheet pack SP due to the flexure caused by the paper folding plate 466 pushing the sheet pack occurs only from the direction of the rear edge of the sheet pack SP that is not fixed, and the folding position is stabilized. As a result, because the sheet pack SP is pushed in in a state that the stitching staple is in contact with the distal end of the paper folding plate 466 constantly, folding processing in which the staple position and the folding position on the sheet pack SP securely coincide with each other can be carried out. Then, after the folding processing is carried out at the central part of the sheet by the folding rollers 451, 452, the sheet pack SP is directly discharged from the nipping part of the folding rollers 451, 452 to the paper discharge tray 301.

As described above, according to the embodiment, sharp folding with good adhesion can be carried out to the sheet pack SP. Thus, the sheet pack SP is firm in the transport direction. Advantages can be provided that the transport accuracy after the folding can be improved and that the loading accuracy to the tray can be improved.

Although exemplary embodiments of the present invention have been shown and described, it will be apparent to those having ordinary skills in the art that a number of changes, modifications, or alterations to the invention as described herein may be made, none of which depart from the spirit of the present invention. All such changes, modifications, and alterations should therefore be seen as within the scope of the present invention. 

1. A sheet post-processing apparatus comprising: a stitching processing unit configured to stitch a sheet pack transported in a transport passage, at predetermined plural positions in along a straight line orthogonal to the direction of the transport with a stitching needle; a pair of folding rollers arranged on a stage following the stitching processing unit in the transport passage, in which large-diameter parts and small-diameter parts of the respective folding rollers are alternately formed symmetrically about the center of the transport passage, and in which facing parts are arranged at the central part in the transport passage so that the small-diameter parts are abutted against the large-diameter parts; and a folding unit having a paper folding plate configured to push the sheet pack into an abutting part of the pair of folding rollers.
 2. The sheet post-processing apparatus according to claim 1, wherein the width of the large-diameter parts and the small-diameter parts of the folding rollers arranged at the central part of the transport passage is set to be smaller than a minimum width of the sheet pack transported in the transport passage.
 3. The sheet post-processing apparatus according to claim 1, wherein the total of the large-diameter part and the small-diameter part formed on each of the folding rollers is three or more.
 4. The sheet post-processing apparatus according to claim 2, wherein the total of the large-diameter part and the small-diameter part formed on each of the folding rollers is three or more.
 5. The sheet post-processing apparatus according to claim 1, wherein the difference in diameter between the large-diameter part and the small-diameter part formed on each of the folding rollers is 2 mm.
 6. The sheet post-processing apparatus according to claim 2, wherein the difference in diameter between the large-diameter part and the small-diameter part formed on each of the folding rollers is 2 mm. 